What causes a deep spot in a river to persist year after year? Underground spring? River is about 6-10 feet deep but this one spot drops to 25 and has been that way for years (straight section of river).

The area gets a lots of day time recreational boat traffic and I have never seen anyone fish the area.

I am thinking about a night trip, to try for some catfish, live and cut perch for bait.

Could be a geologic thing. Maybe there's a strata of sand that washed out. Many strata are slanted so it could be the terminating point of one. Since it is a straight section I wouldn't think scouring alone would do it. Might be a sedimentary change in the soil below that revealed a softer material that washed out.

Maybe a fold in the earths crust that is my laymen s answer to the deep hole, one that let the soft top layer erode away and left the deep buckle to make the hole.
For fishing at night: No light if you can and sit low to the bank do so as to not cast a shadow over the rim Make little noise as possible, use as light as tackle as possible and live bait. Small to large sunfish. Cast some out as far as you can, and bring the others to cover the water column up to 10' out. A Carolina rig or a Texas T will catch fish.
The shovel heads might come up to feed while you are there and make for a great R&R catch. Just about any thing can happen in a spot like that. Big gar, drum,and big cat fish of any kind like to feed on the edge of a deep hole of the river at night, especially on a rise.
BOI, lasers??? That is funny, I wanted to tell you that I caught a small Yiper Bass below the dam yesterday. No pictures however.

I don't claim to know what causes them, but I have found similar places on the Trinity above the lake. I trust the depth finders I have used when I went over them, and the current did crazy things at those points. I visualized cliffs under water.

Don't quote me on this, but I think it's a combination of under water current, sand/mud, one too many river creatures digging the area. Normally current will fill the hole up, but if creatures keep digging into it, then the hole will continue to get larger or stay it's current size.

I know the hole I have caught nice flatheads at night there. I lost a very nice pole and real, there one night. It took off like a rocket and bent the pole holder right over, and the pole shot out and was gone. It was a big fish, I used live bream. There is a lot of clay in the hole I think it feel out in chunks over the years and was washed away. Just my theory.